A two-part exhaust-gas treatment unit for an internal combustion engine is already known, having a base housing and an attachment housing secured to it, from EP 1 691 045 A1. The base housing comprises a SCR catalyst and a DOC catalyst, while the attachment contains two exhaust-gas purification components, a DPF and a SCR. In addition to the inlet and outlet of the base housing as connection site to an exhaust gas system, branch pipes are provided on the base housing for connection of the attachment housing.
From WO 2010/034651 A1 there is likewise known an exhaust-gas treatment unit for an internal combustion engine. This only comprises an exhaust-gas module with an integral housing, in which the exhaust-gas purification components DOC, SCR, DPF and HOH are contained. No further module is provided.
From DE 10 2012 205 350 A1 there is known an exhaust gas purification device consisting of two purification stages A, B. Purification stage A has an inlet and purification stage B has an outlet, while inlet and outlet are each provided at one side surface of the assembled exhaust gas purification device. A separate outlet branch of the first component, which can be connected alternatively to an exhaust tailpipe, is not described. Both purification stage A and purification stage B serve for the purification of the exhaust gas.
From WO 2009/024 815 A2 there is likewise known a two-component exhaust gas after-treatment device. This comprises both an inlet and an outlet. A separate outlet branch of the first component, which can be connected alternatively to an exhaust tailpipe, is not described. The exhaust gas purification system comprises two purification regions. The upper region is determined by the DPF, while the lower region is determined by the SCR catalyst. Both serve for the purification of exhaust gas.
From EP 1 691 045 A1 there is known an exhaust gas treatment system, consisting of a base housing and an attachment housing. The base housing, in turn, has two outlets, wherein one outlet can be connected to the attachment housing, while the second outlet is designed for an exhaust tailpipe. In the base housing are found the SCR and an oxidation catalyst, while in the attachment housing are found the DPF as well as a reduction catalyst.